The Young Try to Improve Health of the Very Young

As the youngest partner at health-care focused investment-management firm Deerfield Management, Alex Karnal, 30 years old, wanted to energize a new generation of philanthropists.

"My group of friends is, thankfully, an extremely generous set of people," Mr. Karnal said, noting that many of them go back to his days as a student at Massachusetts Institute of Technology or have become his friends through the finance industry....